When I stumbled upon scores of studies about the brain differences between PWS' and normal speakers' brains, I also came out this question that are they the cause of the consequence. But stuttering is definitely neurodevelopmental+psychological otherwise you can't explain away the first time when PWS stutter, and no need to explain why it is also psychological. New study also elaborated the neurological cause of stuttering with a new possible model btw: https://www.reddit.com/r/Stutter/comments/xfl3q1/a\_new\_framework\_for\_understanding\_stutteringthe/